JP2005291201A - High recovery sonic gas valve - Google Patents

Abstract

To provide a gas valve that achieves a sonic flow at a lower pressure ratio than in a conventional design.
A high recovery sonic gas valve is provided in which the inlet flow is sideways and enters orthogonally to the outlet flow. This configuration counteracts the effects of the inlet flow entering perpendicular to the nozzle and diffuser axes. The inlet passage is curved so that the flow enters along the centerline of the nozzle and diffuser. This nozzle is contoured and provides an upstream flow obstruction. The diffuser is contoured so that its area gradient changes from a small positive value at the nozzle throat, through a maximum value, and finally to a large drop to almost zero before the nozzle exit. The diffuser is generally cylindrical and may extend beyond the outlet flange of the valve and protrude into the adjacent piping.
[Selection] Figure 2

Description

    The present invention relates generally to gas valves, and more particularly to sonic gas valves.

Accurate control of mass flow is a requirement in many industries. For example, the gas flow is controlled in the equipment industry. In the gas turbine industry, mass flow is used to meter the fuel fed into the gas turbine. The mass flow rate is determined from the following equation.

  Upstream pressure and temperature measurements are used to derive the gas density. In order to measure the speed in the subsonic valve, the downstream pressure is also measured, and the speed is derived based on the pressure difference between the upstream pressure and the downstream pressure. However, this downstream pressure measurement reduces the accuracy and reliability of the flow control due to the use of both upstream and downstream sensors.

  As a result of reduced accuracy and reliability, the industry has developed a sonic gas valve with a Mach 1.0 velocity in the throat (narrowest part) of the valve nozzle. If the gas velocity in the throat is Mach 1.0, the downstream pressure signal cannot propagate upstream through the nozzle throat. This is because the pressure signal cannot travel faster than the speed of sound. One of the results obtained from this is that when the velocity in the nozzle throat is Mach 1.0, the upstream flow flowing into the nozzle is not affected by the downstream pressure. Therefore, even if the downstream pressure is reduced, the speed in the nozzle throat is not affected. As a result, downstream pressure measurements are no longer necessary for speed determination.

  The sonic flow (that is, the gas velocity is Mach 1.0) can be more easily achieved because the inlet side piping and the outlet side piping of the valve are in a straight line (for example, both center lines are a common straight line). There is a case. However, the inlet side piping and the outlet side piping of the valve are not aligned in many installations. In a valve in which the inlet side pipe is orthogonal to the outlet side pipe, the gas flow pattern basically turns 90 degrees from the inlet to the outlet. The flow coming in from the side rather than from the center line of the discharge pipe makes the flow in the valve non-uniform around the nozzle throat. As a result, achieving sonic flow becomes more difficult and higher pressure drops are required to achieve sonic flow. This high pressure drop can cause significant energy loss and can adversely affect the efficiency of the system.

  The present invention provides a gas valve design that achieves sonic flow in a variable area critical (sonic) venturi design with a lower pressure ratio (P1 / P2) than in conventional designs. This valve design provides a curved flow path for the inlet passage and produces a flow condition very similar to each point around the circumference of the nozzle flow region annulus in a more uniform manner. Force into the area.

  The present invention further provides a narrowed throttle located upstream of the nozzle throat to straighten the flow. This narrow shaped aperture starts with an area gradient of approximately zero (eg, a slightly negative gradient), and the negative gradient increases as it approaches the nozzle throat.

  The shape of the diffuser downstream of the nozzle is such that the area gradient starts with a small positive value and increases, then increases to the maximum value and then decreases at the exit of the diffuser, where the channel shape is approximately cylindrical. Has been made. A portion of the axial length of the maximum diameter position of the diffuser portion has a substantially zero area gradient. In one embodiment, when installed, the diffuser portion extends and projects through the valve outlet flange into the adjacent piping.

  These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.

  While the invention will be described in connection with certain preferred embodiments, there is no intent to limit the invention to such embodiments. On the contrary, it is intended to include all alternatives, modifications, and equivalents included within the spirit and scope of the invention as defined by the appended claims.

  The present invention reduces gas (including air) flow and / or fuel flow for industrial or gas turbines, which counteracts or greatly reduces the effect on inlet flow that is orthogonal to the axis of the valve nozzle and diffuser. A gas control valve or other flow control system to control is provided. Some measures to optimize the critical pressure ratio will need to be explained. The critical pressure ratio of the valve (P1 / P2) is defined as the ratio of the inlet pressure (P1) to the outlet pressure (P2), and the flow rate of the valve at this outlet pressure drops to a few percent below the sonic flow rate. Any gas valve will produce a Mach 1.0 sonic flow in the throat of the valve as its pressure ratio (P1 / P2) exceeds approximately 2.0 (depending on gas characteristics). . The valves described herein using the features described above provide sonic flow across the nozzle throat in one embodiment with a pressure ratio (P1 / P2) of approximately 1.04 or greater. Some of these techniques may be applied to other types of valves, including liquid valves, to reduce losses and increase maximum flow. In the embodiment described here, the cross section of the flow path is substantially circular, and the flow path in the valve has a bend of 90 degrees. Such features and strategies can be found in other channel cross-sectional shapes, such as rectangular cross-sections, and straight flow paths, or in the typical ball valve design where the inlet and outlet flanges are aligned and perpendicular to the nozzle centerline. The present invention can also be applied to other flow path shapes and subsonic valves.

  Referring now to the drawings wherein like numerals refer to like elements, an exemplary embodiment of a gas control valve 20 according to the present invention is shown in FIG. As will become apparent from the following description, the gas control valve 20 is a valve that minimizes or cancels the effects of incoming flow that is orthogonal to the axis of the valve nozzle and diffuser.

  1 to 4, the valve body 20 includes a gas inlet 24, a gas outlet 26, and a nozzle throat 28 for the valve needle 30. Actuator 22 may be any type of actuator that controls the movement of valve needle 30 relative to nozzle throat 28. The actuator itself is widely known and need not be discussed in detail here. The valve needle 30 has a contoured surface 32 shaped to provide the desired gas flow versus actuator piston stroke (ie, position). The flow path indicated by the arrow 34 is a curved flow path in the inlet passage 36 and forces the inlet flow into the nozzle 38 more uniformly. The nozzle 38 produces a converging flow where the channel cross-sectional area decreases along the flow direction. This curved flow path helps counteract the effects of inlet flow perpendicular to the nozzle and diffuser axes by changing flow in a direction parallel to the nozzle centerline at a location upstream of the nozzle throat 28.

  The flow cross-sectional area of the inlet channel has a smaller flow area than the cross-sectional area of the upstream inlet-side piping, thereby forcing the flow in the desired direction. Larger cross-sectional inlet channels can also be used, but may allow flow to follow a less favorable path. Smaller flow cross-sectional areas can be applied to significantly reduce losses in other types of valves, including gas valves that are not sonic valves.

  The small cross-sectional area inlet flow path begins adjacent to the upstream pipe 40 in such a manner that the flow path is eccentric with respect to the inlet side pipe 40 such that the inlet flow path is as far as possible from the outlet flange 42 (see FIG. 2). ). This reduces the curvature required for the inlet channel and allows the flow to enter the nozzle region along the nozzle centerline.

  In one embodiment, the cross-section of the inlet channel is non-circular and it is approximately elliptical or the smaller the radius of curvature measured perpendicular to the flow direction is measured parallel to the flow direction. The shape is such that the side of the flow path having the radius of curvature is smaller (see FIG. 8). In either case, the larger dimension measures the flow path corresponding to the long axis of the ellipse orthogonal to the axis of the nozzle center line. This further assists in changing flow in a direction parallel to the nozzle centerline at a location upstream of the nozzle throat 28.

  The arrangement of the inlet side pipe 40 with respect to the outlet side pipe 54 is often restricted by an industry standard. The inlet side piping 40, when measured along the axis of the nozzle and diffuser centerline, should be placed as upstream as possible of the nozzle throat 28 so that the flow enters the nozzle region along the nozzle centerline. The curvature of the inlet channel such that the flow can be changed in a direction parallel to the nozzle centerline at a position upstream of the nozzle throat is beneficial in many embodiments, and for valves with orthogonal inlet piping. It is not limited.

  The narrowed diaphragm 44 is disposed upstream of the nozzle throat 28. The restriction 44 straightens the flow and helps counteract the effects of inlet flow perpendicular to the axis of the nozzle and diffuser centerline. The combined use of the curved inlet passage 36 and the narrowed-shaped restrictor 44 prevents the flow from separating along the shape of the inlet passage and provides a thick boundary layer at the nozzle 38. As the boundary layer becomes thicker, turbulence increases in the diffuser boundary layer, reducing the tendency of the flow to separate from the diffuser wall 46 of the diffuser 48. Turbulence in the diffuser boundary layer helps transfer momentum in the main flow away from the wall and into the diffuser boundary layer, thus increasing the boundary layer velocity and reducing the tendency of the boundary layer to stall and separate .

  The use of the narrowed throttle 44 allows the needle 30 to be further sucked out of the nozzle throat 28 while continuously increasing the gas flow rate, so that the maximum flow rate can be increased. Without such a shape, there is a point where the flow rate does not increase any further as the needle is withdrawn from the nozzle throat. The narrow-shaped stop 44 is shaped such that the area gradient starts with almost zero (for example, slightly negative), and the negative value continuously increases as the nozzle throat 28 is approached. This area gradient is the rate of change of the cross-sectional area per unit length (eg, inches (25.4 mm)) of the axial distance along the flow direction.

  In the diffuser 48, the flow becomes widened, and the cross-sectional area of the flow path increases along the flow direction. The shape of the diffuser 48 downstream of the nozzle 38 is such that the area gradient starts at a small positive value near the nozzle throat 28 and reaches a maximum value and then drops to almost zero at the diffuser outlet 50 where the flow path is It is almost cylindrical. The end of the diffuser may be a cylindrical or substantially cylindrical tube 52 (ie, a tube with a substantially constant cross-sectional area). In one embodiment, the cross-sectional area of the diffuser sleeve is initially reduced immediately downstream of the nozzle throat 28 and has a moderately high curvature in the direction along the flow direction. This medium-high curve shape is continuous, and accordingly the cross-sectional area increases toward the outlet flange 42 at an axial position along the flow direction in the diffuser. In the vicinity of the diffuser outlet 50, the curvature of the wall surface is medium and low, and the area gradient is reduced until the wall surface becomes substantially cylindrical.

  By forming the diffuser 48 so as to have a small area gradient immediately below the nozzle throat 28, the minimum inner diameter of the diffuser wall 46 comes downstream of the nozzle throat. This shape makes the stroke shorter for a valve in which the increase in flow rate per unit length from which the valve needle 30 is pulled out from the nozzle sleeve is substantially linear while maintaining a good critical pressure ratio with a small valve opening. be able to.

  The axial length of the largest diameter portion of the diffuser 48, where the area gradient at the end is approximately zero (substantially cylindrical), is maximized, but this is adjacent piping 54 that extends downstream beyond the valve outlet flange. You may make it protrude in (refer FIG. 2). The extension 52 is substantially cylindrical and may be in contact with the diffuser at the outer flange position, or it may have a slightly larger diameter due to an outward step provided radially at the end of the diffuser. The length L of the extension 52 is not important. The function of the extension 52 is to help maintain the gas flow discharge direction in line with the nozzle 38. In one embodiment, the axial length is 4 inches (101.6 mm) for 6 inch (152.4 mm) diameter inlet and outlet piping valves. This function of the extension 52 can also be designed so that the length of the beginning of the outlet pipe 54 is a reduced diameter that is equal to or slightly larger than the outlet diameter of the diffuser.

  Needle 30 has a length-to-diameter ratio of less than 1 or approximately 1 and has a generally cylindrical or slightly tapered region 56 immediately upstream of the axial position where the taper that provides the flow-to-stroke characteristics of valve 20 begins. Have. This shape prevents the flow from splitting along the inlet side of the needle and provides a thick boundary layer along the needle. This thick boundary layer increases the turbulence in the diffuser boundary layer and reduces the tendency of the flow to separate from the needle wall protruding into the diffuser 48 downstream of the nozzle throat 28.

The needle 30 makes contact with the nozzle throat region 28 of the nozzle 38 by using a conical step 58 ₁ (see FIG. 4b) or a spherical step 58 ₂ (see FIG. 4c) at its outer diameter, and the valve is fully closed. The gas flow is shut off at the position. FIG. 6 shows the blocking by the conical step 58. It can be seen that step 58 is firmly in contact with the portion 28 ₁ of the nozzle throat 28. The radial height of this step 58 is minimized to avoid flow separation, so that the flow boundary layer developed in the generally cylindrical or slightly tapered region 56 is not dissipated and is downstream of the step 58. The thickness of the boundary layer is increased along the plug. In one embodiment, the length-to-diameter ratio of the generally cylindrical or slightly tapered region 56 is approximately equal to 1 (see FIG. 7b).

  The needle stem diameter in the region 60 upstream of the generally cylindrical region 56 is reduced. This reduction in stem diameter minimizes the vorticity of the flow passing by the needle stem 62 and through the nozzle throat opposite the inlet flow piping. A tapered transition 68 is used between the stem diameter and the generally cylindrical or slightly tapered region 56 to avoid flow separation.

  Figures 7a to 7c show different embodiments of valve needles that can be used with the valve 20 of the present invention. FIG. 7a shows a generally cylindrical or tapered region with a short length (length to diameter ratio of less than 1). Figures 7b and 7c show two embodiments in which the length to diameter ratio of the generally cylindrical or slightly tapered region 56 is approximately unity.

  At the time of manufacture, machining (for example, lathe processing) is performed to process the shapes of the nozzle throat 28, the narrowed shape diaphragm 44, and the diffuser 48. Depending on the manufacture of the valve, there may be a misalignment between the machining, where the surface becomes discontinuous where the machining is combined. In one embodiment, in machining the nozzle / diffuser sleeve 64, discontinuities as parts are placed due to machining misalignment, but the cut portion of material removed from both ends is possible with the nozzle throat 28. Arranged as far upstream as possible. This tolerance is the outward step 66 (see FIG. 5), and the diameter downstream of the discontinuity is greater than the diameter at the discontinuity, so the gas flow flows like a waterfall and this larger one Enter the diameter section.

  The technology to improve the flow in the valve was explained. These techniques improve flow performance within the valve. The described techniques may be used individually or in combination. For example, the reduced needle stem diameter, narrowed aperture, diffuser extension, and area gradient pattern techniques can be used for any type of valve, either alone or in combination.

  The use of nouns and similar directives in the context of describing the present invention (especially in the context of the claims) is intended to include both the singular and the plural unless specifically indicated otherwise or clearly denied by the context. It should be interpreted as including. The use of any examples or exemplary terms provided herein (eg, “etc.”) is merely intended to facilitate the description of the invention and is not specifically recited in the claims. As long as it does not limit the scope of the present invention. No language in the specification should be construed as indicating an element that is not included in the scope of the basic claims for carrying out the invention.

  The foregoing descriptions of various embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to be exhaustive and is not intended to be limited to the precise embodiments disclosed. For example, many shapes and techniques can be used for subsonic valves. Many modifications and variations are possible in light of the above teaching. The discussed embodiments provide the principles of the invention and the best description of its practice, and those skilled in the art will recognize the invention in various embodiments as well as specific considerations. It can be used with various changes according to the purpose of use. All such changes and modifications are included within the scope of the present invention as defined in the appended claims when interpreted in accordance with the scope of rights granted fairly, legally and fairly.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several aspects of the present invention and, together with the following description, clarify the principles of the invention. In the drawing
FIG. 1 is a plan view of a sonic gas valve according to the present invention in which a conventional actuator mechanism is mounted on the top of the valve. 2 is a cross-sectional view of the sonic gas valve of FIG. FIG. 3 is a partial cross-sectional view of the valve of FIG. 1 in the closed position, where the valve needle is not in cross-sectional view. 4A is a partial cross-sectional view of the valve of FIG. 1 in a partially open position, where the valve needle is not in cross-sectional view. FIG. 4 (b) is an enlarged cross-sectional view of the valve along 4b, 4c of FIG. 4 (a) showing a conical step according to the teachings of the present invention. FIG. 4 (c) is an enlarged cross-sectional view of the valve along 4b, 4c of FIG. 4 (a) showing a spherical step according to the teachings of the present invention. FIG. 5a is an enlarged view of the narrowed aperture of the valve according to the teachings of the present invention. FIG. 5b is an enlarged view of the narrowed-shaped stop, taken along 5b of FIG. 5a, showing where there is an acceptable discrepancy between machining in accordance with the teachings of the present invention. FIG. 6 is an enlarged cross-sectional view of the valve taken along section 6 in FIG. 7 (a) -7 (c) illustrate an embodiment of a valve needle according to the teachings of the present invention. FIG. 8 is an isometric view of a curved channel in accordance with the teachings of the present invention.

Explanation of symbols

20 Gas control valve 22 Actuator 24 Gas inlet 26 Gas outlet 28 Nozzle throat 30 Valve needle 32 Contour surface 36 Inlet passage 38 Nozzle 40 Inlet side piping 42 Outlet flange 44 Narrowed throttle 46 Diffuser wall 48 Diffuser 50 Diffuser outlet 52 Cylindrical or Almost cylindrical tube (extension)
54 Outlet side pipe 56 Nearly cylindrical or slightly tapered area 58 Step 60 Area upstream of the substantially cylindrical area 62 Needle stem 64 Nozzle / diffuser sleeve 66 Outward step 68 Taper transition

Claims (44)

An inlet having an inlet passage;
A nozzle region in fluid communication with the inlet passage, the nozzle region having a nozzle throat and a narrowed aperture upstream of the nozzle throat;
An outlet in fluid communication with the nozzle throat;
Control valve body. The outlet has a diffuser, and the diffuser has an area gradient that increases from an initial starting position near the nozzle throat to a maximum value and decreases to zero at the outlet boundary,
The valve body according to claim 1. The inner diameter of the initial starting position is smaller than the inner diameter of the nozzle throat, and the initial starting position is downstream of the nozzle throat;
The valve body according to claim 1. The outlet has an outlet flange, and the diffuser extends beyond the outlet flange;
The valve body according to claim 2. The narrowed aperture is shaped such that its area gradient starts at approximately zero and the negative gradient increases as it approaches the nozzle throat.
The valve body according to claim 1. The inlet passage has a curved flow path;
The valve body according to claim 1. The cross-section of the inlet passage is measured in parallel to the flow direction from the side of the flow path having the larger radius of curvature measured in parallel to the flow direction. Is formed so that the side of the flow path having the smaller radius of curvature is smaller,
The valve body according to claim 6. The inlet passage has a substantially oval cross section,
The valve body according to claim 6. The inlet is adapted to connect to an inlet-side pipe having a cross-sectional area, and a cross-sectional area of the inlet passage at a position adjacent to the inlet is less than a cross-sectional area of the inlet-side pipe;
The valve body according to claim 1. The inlet passage is adjacent to the inlet side pipe so that the flow path at a position adjacent to the inlet is as far as possible from the outlet flange of the outlet so that the flow path is eccentric with respect to the inlet side pipe. Begins,
The valve body according to claim 9. In addition, the valve needle is adapted to be movable between a shut-off position and a closed position, the valve needle having a generally cylindrical region upstream of the axial position that begins to taper to provide a flow-to-stroke characteristic of the valve body. Have;
The valve body according to claim 1. The generally cylindrical region has a length to diameter ratio of less than 1 and approximately 1;
The valve body of claim 11. The valve needle has one of a conical step and a spherical step on the outer shape of the valve needle, and the one of the conical step and the spherical step contacts the nozzle throat to fully close the valve. Is adapted to provide a gas flow shut-off at the location,
The valve body of claim 11. The valve needle has a valve stem;
The diameter of the valve stem is smaller than the diameter of the substantially cylindrical region at a position upstream of the substantially cylindrical region;
The valve body of claim 11. And a tapered transition between the small diameter valve stem and the substantially cylindrical region,
The valve body of claim 14. Further, an outward step for allowing inconsistency between machining is provided in the narrowed-shaped aperture.
The valve body according to claim 1. An inlet having an inlet passage;
A nozzle region in fluid communication with the inlet passage, the nozzle region having a nozzle throat;
An outlet in fluid communication with the nozzle throat;
A valve needle adapted to move between a closed position in contact with the nozzle throat and an open position spaced from the nozzle throat, wherein the valve needle begins to taper and the flow of the valve body A valve needle having a substantially cylindrical region upstream of the axial position providing anti-stroke characteristics;
valve. The generally cylindrical region has a length-to-diameter ratio of less than 1 and approximately 1.
The valve of claim 17. The fuel inlet is orthogonal to the fuel outlet;
The valve of claim 17. The inlet passage is curved, thus forcing the inlet flow towards the nozzle in a more uniform manner;
The valve of claim 19. The curved channel and the narrowed-shaped restriction are adapted to prevent flow from separating along the inlet passage and to provide a relatively thick boundary layer at the nozzle.
21. The valve of claim 20. And further comprising a narrowed-shaped stop upstream of the nozzle throat, wherein the narrowed-shaped stop is shaped such that its area gradient starts slightly negative and increases toward the nozzle throat.
The valve of claim 17. The area gradient is shaped in such a way that the area gradient first curves inwardly and then curves outwardly.
23. The valve of claim 22. The valve needle has one of a conical step and a spherical step on the outer shape of the valve needle, and the one of the conical step and the spherical step is when the previous valve needle is in a fully closed position. Made to contact the nozzle throat so as to provide a hermetic shut-off,
The valve body of claim 17. The valve needle has a valve stem, and the diameter of the valve stem is the diameter of the substantially cylindrical region so as to minimize the vorticity of the flow through the valve stem and opposite the inlet passage. Smaller,
The valve body of claim 17. And a tapered transition between the small diameter valve stem and the substantially cylindrical region.
The valve body of claim 25. An inlet configured to connect to an inlet side pipe, the inlet having a curved inlet passage having a smaller cross-sectional area than a cross-sectional area of the inlet side pipe;
A nozzle region in fluid communication with the inlet passage and having a nozzle throat;
An outlet in fluid communication with the nozzle throat;
A valve needle adapted to be movable between a closed position contacting the nozzle throat and an open position spaced from the nozzle throat;
valve. The cross-sectional area of the curved inlet passage is adjacent to the inlet-side piping so that the gas passage is eccentric with respect to the inlet-side piping so that the inlet passage is as far as possible from the outlet flange of the fuel outlet. Starting with
28. The valve of claim 27. The cross-sectional area of the curved inlet passage is such that the radius of curvature measured perpendicular to the flow direction is parallel to the flow direction from the side of the flow path having the larger radius of curvature measured parallel to the flow direction. Molded so that the side of the channel with the smaller radius of curvature to be measured is smaller,
28. The valve of claim 27. A cross-sectional area of the curved inlet passage is substantially elliptical;
28. The valve of claim 27. The outlet has a diffuser, and the diffuser is shaped so that its area gradient increases from an initial starting position near the nozzle throat to a maximum and drops to approximately zero at the fuel outlet boundary.
28. The valve of claim 27. The inner diameter of the initial starting position is smaller than the inner diameter of the nozzle throat, and the initial starting position is downstream of the nozzle throat;
32. The valve of claim 31. Further, a narrowed diaphragm is provided between the nozzle throat and the curved inlet passage.
28. The valve of claim 27. The narrowed aperture is shaped such that its area gradient starts from approximately zero and the negative gradient increases as the narrowed aperture approaches the nozzle throat.
34. The valve of claim 33. An inlet adapted to connect to the inlet side piping and having a curved inlet passage;
A nozzle region in fluid communication with the inlet passage and having a nozzle throat and a narrowed throttle upstream of the nozzle throat;
An outlet in fluid communication with the nozzle throat, the outlet having a diffuser, the diffuser having an area gradient that increases from an initial starting position in the vicinity of the nozzle throat to a maximum value at the boundary of the outlet; Said exit adapted to be shaped to drop to zero;
A valve needle adapted to move between a closed position in contact with the nozzle throat and an open position spaced from the nozzle throat. A valve needle having a substantially cylindrical region upstream of the resulting axial position;
valve. The generally cylindrical region has a length-to-diameter ratio of approximately 1 and less than 1;
36. The valve of claim 35. The narrowed aperture is shaped so that its area gradient starts at approximately zero and the negative gradient increases as it approaches the nozzle throat,
36. The valve of claim 35. The inner diameter of the initial starting position is smaller than the inner diameter of the nozzle throat, and the initial starting position is downstream of the nozzle throat;
36. The valve of claim 35. The cross-sectional area of the curved inlet passage is adjacent to the inlet side piping so that the gas passage is eccentric with respect to the inlet side piping so that the inlet passage is as far as possible from the outlet flange of the outlet. Begins,
36. The valve of claim 35. The cross-sectional area of the curved inlet passage is such that the radius of curvature measured perpendicular to the flow direction is parallel to the flow direction from the side of the flow path having the larger radius of curvature measured parallel to the flow direction. Molded so that the side of the channel with the smaller radius of curvature to be measured is smaller,
36. The valve of claim 35. The inlet is adapted to connect to an inlet-side pipe having a cross-sectional area, and the inlet passage has a cross-sectional area smaller than that of the inlet-side pipe at a position near the inlet;
36. The valve of claim 35. The diffuser extends beyond the outlet flange of the outlet;
36. The valve of claim 35. The initial length portion of the outlet side pipe connected to the diffuser has an inner diameter that is smaller than the inner diameter of the outlet side pipe, thus extending the diffuser.
36. The valve of claim 35. In addition, an outward step is provided in the narrowed diaphragm to allow for discrepancies between machining.
36. The valve of claim 35.

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